Design, implementation and dissemination of effective school-based prevention programs are critical to addressing the childhood obesity epidemic. Currently few successful models exist for the prevention of childhood obesity. Interventions involving just one influencing factor may not have the desired strong independent effects on children's obesity related behaviors, but may contribute to behavior change if integrated with other individual, social, and environmental changes. This study seeks to evaluate the synergistic impacts of integrating an elementary school-based environment and curriculum intervention on children's obesity related behaviors. This research also examines whether the effects of the intervention on children's physical activity vary by gender, ethnicity, and weight status and whether they extend to outside of school time. The proposed environment and curriculum intervention consists of three components: (1) extensive playground renovations, (2) SPARK Active Recreation implemented on the playground during recess, and (3) and an energy balance curriculum implemented during physical education classes. This study employs a 2 (environmental intervention vs. no environmental intervention) x 2 (curriculum intervention vs. no curriculum intervention) factorial design at 18 inner-city ethnically diverse elementary schools with repeated measures (pre-program, mid-program, immediate post-program, and one year post- program) and random assignment to the curriculum intervention. The environmental intervention, or Learning Landscape Initiative, has transformed school playgrounds into attractive and safe multi-use playgrounds tailored to the needs and desires of the local community. The curriculum intervention entails the combination of the SPARK Active Recreation and Balance First curricula and will be delivered for 8 weeks in the fall and 8 weeks in the spring over the two intervention years. This project design will be implemented in two waves. Wave one (with 3 sites from each study condition) will run from year 1- year 4, and wave 2 (with 3 sites from each study condition) will run from year 2-5. Prior to randomization, 12 Learning Landscape elementary schools will be matched to 12 non-Learning Landscape elementary schools according to the percentage of students receiving free or reduced lunch, student's race and ethnicity, and school size. Six of the matched pairs will be randomly assigned to the curriculum intervention. The study aims will be evaluated with objective physical activity measures using SOPLAY (System for Observing Play and Leisure Activity in Youth) measured at baseline (year 1) and years 2, 3, and 4 for wave 1 and years 2-5 for wave 2. The following objective and subjective assessments will also be collected: (1) A random sub-sample of study participants will be selected to wear accelerometers and provide weight and height measurements at baseline and years 2, 3, and 4 for wave 1 and years 2-5 for wave 2 (n=500). (2) A random sub-sample of grade 4 and 5 student's will be assessed on mediating variables and self-reported leisure time physical activity at baseline and years 2, 3, and 4 for wave 1 and years 2-5 for wave 2 (n=580). (3) Playground environmental characteristics (e.g., spatial proximity of activity areas and size, number, type and quality of activity areas) will be measured at the 18 schools through GIS mapping and direct observation characteristic coding.